The primary emphasis in genetic modification has been directed to prokaryotes and mammalian cells. For a variety of reasons, plants have proven more intransigent than other eukaryotic cells to genetically manipulate. However, in many instances, it is desirable to effect transcription of an introduced nucleotide sequence of interest either specifically or preferentially in a particular plant part or at a particular developmental stage of the plant. Accordingly, there is a substantial interest in identifying transcriptional control sequences, such as promoters or enhancers, which specifically or preferentially direct transcription in particular plant organs, tissues or cell types or at particular developmental stages of the plant.
Expression of heterologous DNA sequences in a plant is dependent upon the presence of an operably linked transcriptional control sequence, such as a promoter or enhancer, which is functional within the plant. The choice of transcriptional control sequence will determine when and where within the organism the heterologous DNA sequence is expressed. For example, where continuous expression is desired throughout the cells of a plant, constitutive promoters are utilised. In contrast, where gene expression in response to a stimulus is desired, an inducible promoter may be used. Where expression in specific tissues or organs is desired, a tissue-specific promoter may be used.
Frequently, it is desirable to effect expression of a DNA sequence in particular tissues or organs of a plant. For example, increased nutritional value of a plant might be accomplished by genetic manipulation of the plant's genome with a seed-preferred promoter operably linked to a heterologous gene such that proteins with enhanced amino acid content are produced in the seed of the plant.
Alternatively, it might be desirable to inhibit expression of a native DNA sequence within particular plant tissues to achieve a desired phenotype. In this case, such inhibition might be accomplished by transformation of the plant with a tissue-specific promoter operably linked to an antisense nucleotide sequence, such that expression of the antisense sequence produces an RNA transcript that interferes with translation of the mRNA of the native DNA sequence.
Thus, isolation and characterisation of seed-specific or seed-preferential transcriptional control sequences, which can serve as regulatory regions for expression of heterologous nucleotide sequences of interest in a seed, would be desirable for use in the genetic manipulation of plants.
Reference to any prior art in this specification is not, and should not be taken as, an acknowledgment or any form of suggestion that this prior art forms part of the common general knowledge in any country.